southpark

doubtful

mayor of imaginationland seemed based more off of a circus ringmaster than anything else

the concept of balloon oriented airships is hardly something originating from baron munchausen

not saying trey and matt might not have seen the munchausen movie in the past and based things off of it (imaginationland in particular)

but on-hand visual face-value hardly implies that

I doubt it but it is possible since trey and Matt are big Terry Gilliam fans.